Gun-barrel



.l. T. THOMPSON.

GUN BARREL.

APPLICATION FILED JUNE 30. me.

Patented Feb. 3, 1920.

LSQQAMEQ LSQQAM.

JOHN TALIAFERRO THOMPSON, 0F NEWPORT, KENTUCKY.

GUN-BARREL.

Application filed June 30, 1918. serial No. 307,739.

To all whom/it may concern:

Be it known that I, JOHN 'IALIAFERRO TnoMrson, citizen of the United States of America, and resident of Newport, in the county of Campbell and State of Kentucky, have invented new and useful Improvements in Gun-Barrels, of which the following is a specification.

This invention relates to guns and more particularly to an improved rifled barrel for a gun.

In firearms provided with rifling it has been customary to rifle the barrels throughout their entire length and to employ projectiles which are somewhat larger than the bore of the barrels so that the projectiles will be caused to sink into the rifling and will be subjected to the rotative effect of the riding throughout substantially the entire length of the barrels. This construction has a number of disadvantages, chiefof which are the following: ()wing to the fact that the projectile is somewhat larger than the bore of the barrel there is an excessive amount of friction between the projectile and the barrel. This results in a loss of velocity of the projectile, rapid heating of the barrel, undue wear on the barrel, etc., etc. The wear on the barrel is so great in fact that the rifling soon becomes inefl'ective and the life of a gun is thereby rendered exceedingly short, especially in comparatively high-power guns. The heating of the barrel is very troublesome owing to the fact that it endangers the hands of the user and necessitates his continually guarding against contact therewith, this trouble being particularly pronounced} inrapid fire guns such as automatic and semi-automatic guns.

Moreover, in automatic and semi-automatic guns where the breech action is controlled by the breech pressure andwhere it is essential to the uniform and reliable op- ;eration of the guns that the breech pressure developed at each firing be substantially'thesame, the aforesaid construction is particularly unsatisfactory for the following reasons: With the projectile larger than the bore so that the rifling will bite thereinto, the resistance offered to the successive projectiles in passage through the bore is widely variable, due principally to variations in the size of the projectiles, to the rapid heating and consequent ex ansion of the barrel, to the rapid fouling o the bore.

Ihe wide variation in the resistance to the v of the barrel at Patented Feb. 3, 192d.

successive projectiles produces a corresponding variation in the breech pressure reacting on the breech action, resulting in a nonuniform action of the breech closure and 1n some cases in a complete failure of the breech mechanism to function. For example, if the breech action is adjusted to operate properly with a certain breech pressure, the breech may open too quickly or too forcibly if the reacting pressure increases due to the aforesaid variable factors, or the breech may open too slowly or vnot sufficiently if the reacting pressure decreases.

The object of the present invention is to overcome the aforesaid and other objections to guns of the character referred to. More particularly the object of the invention is to increase the velocity of projectiles in rifled guns, at the same time giving the projectiles sufficient rifling effect to aflord accurate firing, to decrease the heating and wear of the barrel, to decrease fouling of the barrel, and in the case of automatic guns to render the operation of the breech action uniform and reliable.

In one aspect the invention comprises a gun barrel having a bore which is smooth throughout a portion of its length and which is rifled throughout a portion of its length, the grooves of the rifiing having a diameter greater than the diameter of the smooth bore throughout at least a part of said rifled portion and the lands between constricted portion, the constricted portion preferably being confined to a short length the muzzle end and the rifling preferably being confined to the constricted portion. The bore of the barrel, other than the said portion, is preferably substantially equal in diameter to the diameter of the projectiles so that the projectiles will pass freely therethrough until they reach the constricted portion when they will be subjected to therifling effect just before leaving the barrel. The ritling grooves preferably begin at substantially'zero depth at the beginning of the constricted portion and gradually increase in depth throughand is provided with rifling throughout the firing cham portion 3 by which the barrel may be at-' out the constricted portion. Owing to the gradual constriction of said portion no shoulder or sudden change in resistance is afforded to the projectiles and owing to the gradual deepening of the rifling grooves the projectiles are set into rotation more gradually. The gradual increase in the depth of the rifling grooves is so pro portioned to' the gradual constriction of the ore that the cross-sectional area of the bore is maintained substantially constant throughout said constricted portion of the bore and substantially equal to the diameter of the cylindrical portion of the bore, whereby when the projectiles pass through the constricted portion they may gradually extrude into the rifling grooves and not be materially retarded by the constriction.

I am aware that it has been proposed to repair firearms in which the rifling has been worn away by renewing the rifiing only.

throughout a portion of the bore, and the present invention is not to be confused with any such expedient.

In order more clearly to set forth my invention I have illustrated one concrete embodiment thereof in the accompanying drawin s, in which igure 1 is a longitudinal section through my improved gun-barrel; i

Fig. 2 is an enlarged section of the barrel at the muzzle end showing the constricted portion of the bore prior to the cutting of the rifling grooves; and

Fig. 3 is an enlarged section of the barrel at the muzzle end showing the constricted portion of the bore after the rifling grooves have been cut.

Referring to the drawings, a gun-barrel is shown at l rovided at the breech end with a r 2 and an exteriorly threaded tached to a receiver (not shown). The bore 4 of the barrel is finished smooth from the chamber 2 to a point preferably from three to twelve inches from the muzzle end of the barrel and with 1 a diameter substantially equal to that of the bullet which in a service rifle is .308 inches.

At the muzzle end the hole is tapered or constricted gradually as at 5- until at the muzzle the diameter of thebore is reduced as for example to .300 inches. In this constricted region of the bore rifiing grooves 6 are formed, the grooves beginning at the beginning of the constricted portion and ex- The grooves begin at substantially zero depth I I and gradually increase in depth. The number of grooves and the pitch of their spiral may be determined in accordance with usual pract1ce. Preferably the grooves are tapered in depth reverse to the taper of the constricted portion 5 of the barrel so that at the muzzle the diameter of the bore at the tidn of the bore. Therefore when a bullet ente'rs the constricted portion 5 of the bore the metal which is gradually extruded from the bullet due to the pressure exerted upon it by the tapered wall of the bore finds an increasing amount of space through the constricted portion. No axial deformation of the bullet is caused by the constriction of the bore but merely a radial-displacement, and toa slight extent a circumferential displacement, of the cylindrical surface of the bullet. With this construction the bullet secures a-good on the rifling and the necessary rota tion of the bullet is assured.

In Fig. 2 I have shown, on an enlarged scale, the muzzle end of a gun provided with a bore constricted as at 5. For'clearness of illustration the bore is shown in the condition which it assumes prior to the formation of the rifiing grooves, the depth to which the grooves are to be out being indicated by dot and dash lines. It is to be especially noted that the mergence of the constricted portion of the bore into the the smooth portion 4 of the bore is very gradual and therefore no sudden retardation of the bullet which might tend to explode the barrel is occasioned.

From the preceding descriptionit will appear that the diameter of the grooves of the rifling (the diameter of the dot and dash lines in Fig. 2) is greater than the diameter of the smooth bore and that'the diameter of the lands between the rifling grooves (the diameter of the constricted portion of the bore) is less than the diameter of the smooth bore, which if extended throughout the entire length of the barrel would have a diameter of the dotted lines in Fig. 2. While I have shown the rifling grooves increasing in diameter toward the muzzle this diameter may be constant or even decreasing toward the muzzle depending upon the type of projectile and type of gun used.

From the foregoing description it is apparent that I have provided an improved gun which, because of its smooth bore and small extent of'rifling, permits the bullets to be discharged at a greater velocity withthe same amount ofpowder charge; which, because of the smooth bore. has less friction between the bullets and the bore and. as a consequence, less heating of the barrel, less higher velocity of the bullets, causes at greater penetration. Where my improved barrel is employed on automatic or semiautomatic guns, the features herein set forth are' particularly advantageous, as a more uniform breech pressure upon Which guns of this type depend for their functioning, results from a more uniform reaction from the bullet.

I claim:

1. A gun barrel having a bore Whose rear- Ward portion is smooth and whose forward portion is rifled, the grooves of therifiing beginning at zero depth and gradually flaring outwardly and the lands of the rifling beginning at zero tapering inwardly. 2. A gun barrel having rifiing grooves throughout a portion of its length, the rifiing grooves beginning. at substantially zero depth and gradually increasing in depth toward the muzzle of the barrel s0 smooth height and gradually that the diameter between the bottoms of opposed rifiing grooves is greater than the diameter of the bore. v

.3. A gun barrel having a bore which is smooth throughout a portion of its length and which isrifled throughout a portion of its length, the grooves of the rifling having a diameter greater than the diameter of said portion of the bore throughout at least a part of said rifled portion. 4. A gun barrel having its bore gradually constricted throughout a portion of its length and having rifiing grooves in the constricted portion, the rifiing grooves beginning at substantially zero depth at the beginning of said portion and gradually flaring outwardly so that the diameter between the bottoms of opposed rifiing grooves gradually increases thereby tocompensate for the constriction.

Signed by me at Boston, Massachusetts,.

this twenty-sixth day of J line 1919. JOHN 'l-ALIAFERRO THOMPSON. 

